1. Field of the Invention
This invention relates to the formation and smoothening (flattening) of a wiring film in the manufacturing process of a semiconductor represented by ultra large scale integrated circuit (ULSI) and, particularly, a method for attaining the smoothening by forming a wiring material film by physical vapor deposition (PVD), chemical vapor deposition (CVD), plating or the like, and treating it with a high pressure gas.
2. Description of the Prior Art
(Prior Art 1)
Japanese Patent No. 2660040 (issued Oct. 8, 1997) discloses "a method of forming a vacuum film which comprises steps of forming a metal thin film on a substrate having a recessed part by a vacuum thin film forming method such as sputtering, CVD, vacuum evaporation or the like; heating the whole metal thin film formed on the substrate to fluidize it; and pressurizing the metal of the fluidized metal thin film by a gas to fill the recessed part with the metal of the metal thin film in such a manner that no cavity is produced within the recessed part".
(Prior Art 2)
Japanese Patent Application Laid-Open No. 7-193063 discloses "a method for processing an article having a surface, the surface having at least one recessed part within the surface, which comprises forming a layer on at least a part of the surface so that the layer is extended above the recessed part, and exposing the article and the layer to a high pressure and high temperature sufficient to deform a part of the layer so as to fill the recessed part". It is described in this known data that the article consists of a semiconductor wafer, the recessed part consists of a hole, groove or via formed on the semiconductor wafer, and the layer consists of a metal such as aluminum. It is also disclosed that a gas is usable for pressurization at a temperature of 350-650.degree. C. and a pressure of 3,000 psi or more when the layer is aluminum, and it is necessary to set the thickness of the layer formed on the hole or groove equal to at least the width of the hole. Further, it is also described that the semiconductor itself, even if a plurality of layers having different characteristics are included therein, can be manufactured as the result of a manufacturing process including a plurality of steps in order to form it.
In a substrate to be treated 1 which is shown by a Si substrate having a hole or groove part 2A formed thereon in FIGS. 1(a), (b), and (c), the surface of a SiO.sub.2 insulating film layer 2 is covered with a metal wiring film 4 through a TiN barrier layer 3.
The first problem of the prior arts is that a filming material must be laid in the state where it perfectly covers the hole or groove at the time of filming as shown in FIG. 1(a) in order to form a texture having no pore in the hole or groove part 2A by pressure filling treatment [FIG. 1(a)]. It is clearly described in the specification of the above Prior Art 2 that this is an essential requirement, and the thickness is also described therein as described above. However, actual grooves or holes have various forms, and it is the actual state that it is difficult to form a film so as to block the opening part while leaving the cavity of the groove or hole by PVD (generally, sputtering), CVD, plating or the like, particularly, when the width of the groove or the diameter of the hole is 0.5 .mu.m or more. When the part having such a groove or hole formed thereon is actually subjected to a filming treatment by these techniques, a recessed part 4A is consequently formed in a metal wiring film 4 as shown in FIG. 1(c). Although it is regarded that the groove or hole in such a state can not be filled by the prior arts, how to treat a wafer having a groove or hole having a large width or diameter is a serious problem in the actual production, setting aside a wafer in which all grooves or holes are laid in the state as shown in FIG. 1(a).
As a method for filling the cavity formed under the wiring film formed in the hole or groove in order to improve the conductivity of a semiconductor wiring film, mainly, for an Al wiring film, it is shown in these prior arts that crush or inflow by a high pressure at a high temperature is effective. However, the Al wiring film shown in these known data reaches the limit in respect to EM resistance (Electron Migration) and reduction in electric resistance which are required as the wiring material according to the fining of ULSI in the future. Although expectations are recently placed on Cu which is regarded to be superior to Al in these respects, the equal result can not be obtained even if the above prior arts are applied thereto in the same manner, since the filming condition and the texture of the film after filming are largely differed from Al, and the state as shown in FIG. 1(a) can hardly be provided when the groove width or hole diameter is 0.5 .mu.m or more.
As a result of experimental examination of the application of the prior arts to a copper wiring film formed mainly by sputtering, the present inventors found the above problems and studied for the solution of the problems to attain this invention.